THE SAN FRANCISCO EARTHQUAKE 



117 



seismological instruments that the writer, while attending the Seventh 

 International Geographic Congress at Berlin, 1899, as a delegate from 

 the Xational Geographic Society, was made a member of the Pro- 

 visional Committee of the International Seismological Association, just 

 organized by the congress. 



The instrumental seismological data referring to the recent San 

 Francisco earthquake will be contributed from the following stations 

 in Canada and the United States: 



Table 1. List of Stations and Institutions in Canada and 

 the United States Contributing Seismological Data. 



The exceedingly sparse distribution of seismological stations in this 

 country is made apparent by this list, there being none in the middle 

 portion of the United States, where, as already stated, regional earth- 

 quakes are comparatively frequent. It is therefore fortunate in the 

 study of the San Francisco earthquake that we may have recourse also 

 to the data afforded by magnetographs, especially by those at Baldwin, 

 Kansas, and Sitka, Alaska — the nearest magnetic observatories to the 

 origin of the quake and situated, as will be seen from Table 3, at 

 about the same distance from San Francisco. So also is it a fortunate 

 circumstance that we have both magnetograph and seismograph data 

 from the two magnetic observatories, Honolulu and Cheltenham, 

 which are also practically equidistant from the origin. 



Xow a peculiar circumstance is that this earthquake, while giving 

 a record on the seismograph at the Porto Eico Magnetic Observatory 

 so large as not to be fully recorded, left no trace behind on a magneto- 

 graph of the very same pattern as at the other observatories. On the 



1 A Bosch-Omori seismograph procured for this observatory was temporarily 

 installed at Baltimore by Professor H. F. Reid for a comparative study with 

 his Milne seismograph. 



